Do, or do not

Make a page that, half of the time, tells you to do something:

Do

The rest of the time, it tells you not to do it:

Do not

It's random. You can try it.

This one's easy. First, add some HTML like this:

<h2>Things to <span id="not">not</span> do</h2>

On page load:

if ( Math.random() > 0.5 ) {
    $("#not").hide();
}

Math.random() returns a random number between 0 and 1.

You can change the test. For example, do not do on a weekday, do on a weekend.